A piece of electronic equipment typically has several electrically conductive exterior surfaces. When the equipment is properly manufactured and maintained, the electrically conductive surfaces are insulated against leakage from the interior circuitry of the apparatus. In the event the insulating barriers between the electrically conductive exterior surfaces and the inner components of an electronic device fail as a result of damage or deterioration, a charge may develope on the conductive exterior surfaces of the apparatus, which could cause injury to an operator and damage to other electronic equipment.
Hospitals and clinics and other medical facilities which use numerous pieces of electronic equipment are regulated by one or more agencies, including the Joint Commission on Accreditation of Health Care Organizations. The Joint Commission has recommended that all hospital electronic equipment with which a patient can come into contact should be tested twice a year for electronic leakage. The Commission has further recommended that equipment used in certain critical areas be tested four times a year.
Some electrical equipment safety standard organizations, such as Underwriter's Laboratories and Canadian Standards Association, have provided a standardized safety test which should be used to detect and measure electrical leakage to the exposed conductive surfaces of a piece of electronic equipment. The standardized safety test recommends that a 1,000 Ohm load be used in parallel with a volt meter to measure any leakage to each conductive outer surface of electrical equipment while four successive tests are applied to the equipment. Such equipment typically has a standard AC plug or male connector with a high voltage contact, a low voltage contact, and ground contact. In the first test, the connector from the equipment is properly attached to a source of AC current, that is, the high voltage side of an AC source is applied to the high voltage contact of the connector, the low voltage side of an AC source is applied to the low voltage contact and the ground of the connector is grounded. In the second test, the high and low sides of a source of AC power are reversed. The high side of a source of AC power is applied to the low voltage contact of the connector, the low side of the source of AC power is applied to the high voltage contact, and the ground contact of the AC connector is grounded. In the third test, the high side of the source of AC power is again connected to the high voltage contact of the connector from the equipment, and the low side of the source of AC power is connected to the low voltage contact of the connector and the ground contact of the male connector is left unconnected. In the fourth test, the high and low sides of the source of AC power are again reversed as in the second test, and the ground contact from the connector left disconnected.
The foregoing tests are conducted by applying AC power for one of the test configurations to the male connector of the equipment to be tested, and thereafter, contacting a probe in series with a resistor and volt meter against successive exterior surfaces of the equipment until all surfaces have been tested for leakage. Thereafter, a second configuration is applied to the connector of the equipment and the probe again contacted against all the exterior surfaces of the equipment. Where the equipment to be tested has a large number of isolated conductive exterior surfaces, as for example, where there are a plurality of metal bolts extending through a wooden chassis, each of the four tests can consume a substantial period of time. As a result of the time consumed to perform all four tests, some hospitals have chosen to omit one or more of the tests, or have chosen to undertake tests less frequently than recommended.
Therefore, it would be desirable to provide a test device which would simplify the testing procedure such that all four of the tests could be made by contacting a probe once to each of the electrically conductive surfaces of the equipment to be tested.